Electric motor system of wire block control



Dec. 29, 1953 w. FEW ETAL ,664,

ELECTRIC MOTOR SYSTEM OF WIRE BLOCK CONTROL Filed Aug. 12. 1948 sSheets-Sheet 1 INVENTORS. WILLIAM FEW AND JOHN D. SAUTER.

ATTORAEX' Dec. 29, 1953 w. FEW ETAL 645 9 ELECTRIC MOTOR SYSTEM OF WIREBLOCK CONTROL Filed Aug. 12, 1948 3 Sheets-Sheet 2 m/Lfl 14 146 125: 164

.115 I L L v 143 I144 INVENTORS. WILLIAM FEW Am:

BY JOHN D. SAUTER.

ATTORJVEY Dec. 29, 1953 w. FEW ETAL 2,664,529

ELECTRIC MOTOR SYSTEM OF WIRE BLOCK CONTROL Filed Aug. 12, 1948 3Sheets-Sheet 3 INVENTORS. WlLLIAM FEW AND JOHN D. SAUTER.

ya- @ZMW AY'TORAFE'Y Patented Dec. 29, 1953 ELECTRIC MOTOR SYSTEM OFWIRE BLOCK CONTROL William Few and John D. Sauter, Cleveland Heights,Ohio, assignors to The Clark Controller Company, Cleveland, Ohio, acorporation of Ohio Application August 12, 1948, Serial No. 43,787

7 Claims.

Our invention relates to methods and apparatus for speed and currentcontrol.

A specific object of the invention is to control relative speeds of wireat successive blocks in a multiple-block wire drawing machine in orderto maintain each portion of the wire continuously at a suitable speedaccording to the draft through each die.

Another object of the invention is to obtain continuous variation ininfinitesimal increments of an electric current in response tovariations in positon of a movable member. More specifically, it is anobject to obtain such current variation in a direct-current circuit suchas, for example, the direct-current winding of a saturable reactor.Furthermore, it is an object to render a saturable reactor, responsivecontinuously in infinitesimal increments to variations in position of adancer arm of a multiple-block wire drawing machine.

Another object of the invention is to avoid hunting in the rotation ofthe capstans of a multiple-block wire drawing machine and to obtaininfinitesimal increments in the adjustment of speed of successivecapstans, so that the dancer arms carrying loops of wire from one die tothe next capstan may remain in a given position, without the necessityfor constant working back and forth to obtain an average speedappropriate to the speed with which the next capstan draws the wirethrough the die.

Still another object of the invention is to enable wire to be drawnthrough multiple-block wire drawing machines at far greater speed thanheretofore, but nevertheless with a high degree of safety; to minimizebreakage of wire, and to obtain very rapid adustment in the speed of thecapstans appropriate to the speed of the succeeding capstans whileavoiding hunting. Generally, an object of the invention is to providesuch improved control of any filar element carried on motor drivencapstans or the like.

Other and further objects, features and advantages of the invention willbecome apparent as the description proceeds.

In carrying out our invention in accordance with an improved embodimentthereof, We utilize manual control of the speed of the motor driving thelast capstan of the series of the multipleblock wire drawing machine,and the speeds of the motors driving the preceding capstans areautomatically adjusted to the proper speed for the speed at which thelast capstan draws the wire through the final die. Separate motors areemplayed fordriving each capstan, and either a g!!- stant voltage,direct-current source may be employed for driving the motors or avariable voltage generator may be provided for energizing all of thecapstan motors.

The motors are preferably compound wound direct-current motors havingseries fields and also having shunt fields. Conventional pivoted dancerarms, upon which are mounted pulleys for carrying the loops of wire fromone capstan to the succeeding die, are provided for controlli the shuntfield excitation of the preceding capstan motor at such a speed that thelength of the loop neither increases nor decreases and the successivecapstan speeds are proportional to the draft of the die betweensuccessive capstans. In

order to obtain continuous speed variations with infinitesimalincrements, to increase the reliability of speed control and therapidity with which adjustments may be made, as well as to increase thesturdiness and life of the apparatus and avoid the difiiculty ofmaintenance of contacts and rheostats, We provide electronic currentcontrol for the shunt fields of the motors.

In the preferred arrangement some of the field current is supplied froma constant potential source through a manually adjustable rheostat,Which is ordinarily left in a fixed position, after the suitableadjustment has been ascertained and the adjustment of variation in fieldcurrent is provided by a phase-responsive rectifier of the gas or vapordischarge type, commonly referred to as a thyratron" type of rectifier.The phase control of the rectifier is made responsive to the angularposition of the dancer arms, each dancer arm being arranged to controlthe field current of the motor driving the preceding capstan. The phasecontrol may be obtained by a suitable phase shifter, such as a bridgetype phase adjustor of the resistance-reactance type, for example, inwhich the magnitude of one of the electrical dimensions is adjusted forchanging the phase. Preferably a saturable reactor is utilized as thereactance arm of the phase adjuster and the phase adjustment isaccomplished by varying the direct-current flow through the directcurrent winding of the saturable reactor. If desired, however, a movablearmature adjustable reactor may be employed in which the armature ismechanically linked to the dancer arm.

Where a saturable reactor type of phase adjustor is employed, anelectronic type of current adjustor is preferable. We have found thatprecise, reliable and rapid adjustment of the directcurrent in asaturable reactor responsive to movement of a movable member. such asthe dancer arm, is preferably obtained by means of a vacuum tube type ofrectifier with anticipating or anti-hunt circuits incorporated in thedegenerative bias thereof, and having control grids ex cited by thesecondary winding of a variable ratio transformer, the ratio of which isdetermined by the relative angular positions of the primary and secondwindings. For example a synchro nous generator of the type sold as aSelsyn motor or generator may the rotor is mechanically linked to thedancer arm of the wire block machine. In order that sensitivityadjustment and adjustment of the.

zero position of the dancer arm may be obtained electrically withoutrequiring any change in mechanical linkage, a bridge type of connectionis preferably interposed between. the secondary winding of the variableratio transformer and the grid circuit of the vacuum tube rectifier.Such bridge circuit includes a sensitivity adjustment potentiometer anda position adjust ment potentiometer, as will be described more indetail hereinafter. Control circuits are also so arranged that fullfield is automatically applied to the capstan motor when the machine isstarted. independent of the position of the dancer arms.

A better understanding of the invention will be afforded by thefollowing detailed description considered in con unction with theaccompanying drawing, in which:

Fig. 1 is a schematic diagram of a multiplemotor multiple capstan wireblock machine in which the dancer arms are arranged for controllingmotor speed in accordance with our invention;

Fig. 2 is a circuit diagram of one form of electrical system which maybe employed for driving the motors shown in Fig. l.- with details of theelectronic field control circuits omitted for clarity in the drawing;

Fig. 3 is a detailed circuit diagram of the field current controlcircuit for one of the capstan driving motors other than the lastcapstan driving motor in accordance with an embodiment of our invention;

Figs. 4a, 4b, 4c and 4d are graphs, which illustrate the principle ofoperation of the vapor dis charge type phase-responsivecurrent-controlling rectifiers indicated in Fig. 2 and shown moreclearly in Fig. 3, and which illustrate the operation for differentpositions of the dancer arm and different operating conditions of thewire block machine; and

Figs. 5a, 5b, 5c, 5d, and 5e are graphs, which illustrate the principleof operation of the vacuum tube type direct-current regulator shown inFig. 3 for regulating the magnitude of the current in the direct-currentwinding of the saturable reactor, and which illustrate the operation fordifierent positions of the dancer arm and different positions of themechanism for adiusting the control voltages of the current regulator.

Like reference characters are utilized throughout the drawing todesignate like parts.

Wire block machines have been produced having dancer arms which operatesliding-contact field resistors for adjusting the speeds of capstanmotors to maintain as nearly as possible constant lengths of the wireloop between one capstan and the succeeding die. such arrangementshaving three or four capstan motors with automatically controlled speedshave been built and maximum wire speeds as high as one thousand feet(1,000 ft.) per minute have been obtained.

be employed in which.

It is an object of our invention not only to enable the speed of wiredrawing to be greatly increased to about three thousand feet (3,000 ft.)per minute, for example, but also to enable wire drawing to beaccomplished efficiently and with-- out dam e rbre k ge in connectionwith materials which are more diflicult to draw, such as very hard wire,wire rope or stainless steel wire and the like. Furthermore, it is anobject to facilitate increasing the amount of drafts which may beobtained with reliable operation. We may, for example, employ six ormore sepa rately controlled capstan driving motors having their speedsautomatically controlled in accordance with, our invention. Forsimplicity, however, in Fig. 1 we have shown an arrangement with onlythree capstan motors which are automatically controlled and a final-drawcapstan motor which is manually adjusted to the desired output speed.The three preceding capstan motors illustrated adjust themselvesautomatically to the proper speeds for obtaining suitable operation ofthe machine in proportion to the speed of the final draw capstan. Themanner in which additional non-illustrated automatically controlledcapstan motors and their field controls would be arranged will beapparent to those skilled in the art.

Referring to Fig. 1, we may, in accordance with frequent practice,employ a first capstan l i having two different drums l2 and I3 so as toobtain a double draw through dies l4 and is in succession. Preferably,however, the succeeding capstans l6 and I1 and iii are driven byseparate motors and each follows a single die so that individualadjustment of the speed of draft through dies l9 and 20 and 28 may beobtained without slippage of wire on any of the capstans. The capstansII, II; and H are driven by motors 22, 23 and 24 respectively, each ofwhich is provided with automatic field control in accordance with ourinvention and the capstan I8 is driven by a motor 25 having manual fieldcon trol by which the output speed of the machine is determined.

A movable pulley carried by a spring-biased dancer arm is provided forcarrying a loop of wire between each capstan and the succeeding die.Thus between the capstan H and the die 19 there is a movable pulley 3!mounted on a dancer arm 32 for carrying a loop of wire 33 passing fromthe drum I3 of the capstan ll around the pulley 3| to the die I9. Forkeeping the wire loop 33 taut, a spring 26 is provided for the arm 32.The dancer arm 32 is pivoted at 34 upon a shaft 35 which is connected orotherwise linked to the rotor, not shown 1n Fig. 1, of an adjustableratio transformer such as a Selsyn 35 for example. Similar spring-biaseddancer arms 31 and 38 mechanically connected to Selsyns 4i and 62 areprovided between the capstan I6 and the die 20 and between the capstanl1 and the die 2|.

For energizing the motors 22, 23, 24 and 25 a constant potential,direct-current source or, if desired, a variable voltage system isutilized having a separate variable voltage generator for energizing allthe motors of the block. For the sake of illustration, the latter typeof system has been represented in Fig. 2, as shown, by a main generator5| supplying the motors 22, 23, 24 and 25 through power conductors 52and 53. A source of substantially constant-potential excit-a ing currentis provided having a positive terminal 54 and a negative terminal 55.The main generator 5| has a field winding 56 energized from thedirect-current source 54 and 55 through suitable field adjustingrheostats or potentiometers, such as the potentiometer 51 as indicated.The same direct-current source 54--55 may be employed, as shown, forproviding a portion of the shunt field current for the motors 22, 23, 24and 25. These motors may, if desired, be of the compound-wound typehaving series fields 58. The motors 22, 23, 24 and 25 also havepotential field windings 59, BI, 62 and 63, respectively, which may becalled shunt field windings by analogy to the conventional connectionfor compound wound motors. The motor 25, having manual speed adjustment,has its field winding 63 supplied entirely from the direct-currentsource 54- 55 through a manually operated field rheostat 64 of theconventional type. The automatically controlled motors 22, 23 and 24have their field windings 59, BI and 82 connected to the source 5455 inseries with manually operated rheostats 65, G6 and 61, respectively.These rheostats 65, 66 and 67, however, are normally left in a fixedposition during operation, and for obtaining field control,supplementary current supply sources 60, 69 and are provided. Thesesources 08, 69 and I0 are of the electronic or vapor-discharge type andare indicated only fragmentarily in Fig. 2. Each of the current supplysources 68, 69 and III, as shown, has positive and negative outputconductors 'II and I2 connected across the motor shunt field winding andpreferably a voltagelimiting discharge resistor 13 is also connectedacross the field winding.

Each of the discharge resistors I3 is composed of a material with theproperty of having a negative voltage coefficient of resistance, so thatthe voltage can rise relatively little above the predetermined valuedetermined by the dimensions and arrangement of the resistor. Theseresistors may consist of so-called Thyrite, or material having thecomposition described in Patent No. 1,822,742, McEachron.

Since the field current controlling devices 68, 69 and I0 are similar, asingle detailed drawing of the complete circuit of one of them is shownin Fig. 3. They are all energized from a source of alternating currentI4, and, if desired, a multiple-secondary transformer having a commoncore and a primary Winding I5 may be provided with separate secondarywind ngs I6, I1 and 1B for the regulators 68, 69 and '10 respectively.As illustrated in Fig. 3 the regulator I0 comprises, in combination withthe transformer having the secondary winding I8, a pair of electricdischarge devices I9 and B0, an excitation phase adiusting circuit 82including a saturable core reactor 83, and a saturation controllingcircuit 84 responsive to the angular position of the dancer arm 38. Thedischarge devices I9 and B0 are preferably of the gas or vapor dischargetype in which current conductivity is maintained, so long as positiveanode potential remains, once the grid or control electrode potentialhas been raised to a predetermined value, regardless of subsequentfluctuations in the grid potential. Such discharge devices are commonlyreferred to as thyratron" tubes and the term thyratron will be usedthroughout the description and claims to refer to this type of electricdischarge device or current controlling device. The thyratrons I9 and 80comprise envelopes containing suitable gas or vapor, and enclosingplates or anodes 85 and 95, cathodes 01 and B8 (heater current sourcesbeing omitted for simplicity), and control eleciii) 6 trodes or grids B9and 90 respectively. In order that full wave rectification may beobtained a pair of thyratrons I9 and is employed but our invention isnot limited thereto.

In the arrangement illustrated, the anodes 05 and B6 are connectedthrough suitable anode resistors 9| and 92 to opposite ends of thetransformer winding I8. The cathodes 81 and 88 are connected to thepositive input conductor 'II of the field winding 62, and the negativeinput conductor 12 of the field winding 82 is connected to a center tap93 of the transformer secondary Winding I9.

The phase adjustor 82 has a pair of variable phase output conductors 94and 95 connected to the control electrodes 89 and throughcurrentlimiting resistors 95.

The phase adjustor 82 in the form illustrated comprises a triangularbridge having a voltage supply arm 91, a resistance arm 98, a reactancearm 99 and a cross arm NH. The input voltage supply arm 91 constitutes asecondary winding of a transformer having a primary winding I02 suppliedwith voltage in the same phase as the voltage I4. For the purpose ofcircuit isolation, preferably a secondary winding I03 is provided on thecore of the transformer I5 for energizing the phase shifter primarywinding I02. For the sake of circuit isolation, also, the cross arm IOItakes the form of transformers I04 having primary windings I05 connectedin parallel, the parallel group being connected at one end to a centertap I06 of the transformer winding 91 and at the other end to a commonterminal N1 of the resistor arm 98 and the reactance arm 99. Thetransformers I04 have secondary windings I 00 and I09 connected in thecontrol electrode circuits respectively of the thyratrons I9 and 80,through the conductors 94 and 95, and a neutral conductor Ila.

The saturable reactor 83 comprises a pair of parallel connectedalternating-current windings forming the reactance arm 99 and adirect-current winding I I I. As will be understood by those skilled inthe art, such saturable reactors commonly comprise three-legged coreswith a directcurrent winding wound on a center core, or an equivalentarrangement with the alternatingcurrent windings connected so as toavoid inducing high voltage in the direct-current winding.

The saturating current controller 04 comprises a pair of high vacuumtubes I I2 and H3 having control electrodes or grids such as triodes6SN7G, e. g., with a plate or anode supply such as a transformer H4, andhaving control voltage supplied by the variable ratio transformer or"Selsyn" 42, energized by the same transformer H4, so as to preservein-phase or out-of-phase relationship between the anodes and the gridsof the tubes H2 and H3.

The tubes H2 and II! are provided with a cathode bias resistor II5shunted by a smoothing condenser I I 8. The capacity of the condenserIE6, however, is sufficiently small so that appreciable degenerativeeffect is obtained. Preferably, anticipating circuits are interposed inthe coupling of the control voltage to the control grids, in order toassist further in avoiding hunting. For example, a differentiatingcircuit may be provided comprising a potentiometer I II and a condenserH8 connected in series across the cathode resistor H5 and an integratingcircuit may be provided comprising a condenser I I9 and a potentiometerI20 connected in series between the cathode terminal I22 and a tap oradjustable contact I23 of the. potentiometer H1. The control voltage maybe interposed between the tap or adjustable contact I24 01 thepotentiometer I and the control grids of the tubes I I2 and I I3, butpreferably the control voltage is supplied through a bridge arrangementI in order that sensitivity adjustment and position adjustment may beprovided.

The tubes H2 and II3 contain anodes I25 and I21, control electrodes I29and I29 and cathodes I3I and I32 respectively. The anodes I26 and I21are connected to opposite ends of a winding I33 forming a secondarywinding in the transformer II4, the primary winding I34 of which may beenergized from the winding I03 in common with the winding I02 of thephase shifting bridge 92. The direct-current winding III of thesaturable reactor 83 is connected between the center tap I35 of theplate transformer winding I33 and the negative end terminal I36 of thecathode resistor H5.

The bridge circuit I25 comprises a supply winding I31 which is anothersecondary winding of the transformer I I3 having a center tap I38, and aposition adjusting potentiometer I39 connected across the winding I31,preferably with resistors MI and I42 connected in series with bothterminals. The cross arm of the bridge I25 com prises a pair of parallelconnected primary transformer windings I43 and I44 connected between anadjustable tap I45 of the potentiometer I39 and an adjustable tap I46 ofa sensitivity-adjustment potentiometer I41 having an end terminal I46connected to the center tap I38 of the winding I31. The windings I43 andI44 constitute primary windings of transformers I48 and I49 havingsecondary windings I5I and I52, respectively. The secondary windings I5Iand I52 have a common terminal I 53 connected to the adjustable tap I24of the potentiometer I20. The free ends of the transformer windings I5Iand I52 are connected through current limiting resistors I54 and I55 tothe control electrodes or grids I28 and I29 of the tubes H2 and H3respectively.

The variable ratio transformer 42 in the form illustrated comprises analternating-current dynamo electric machine having windings both on thestator and the rotor. To avoid unnecessary stocking of special parts. adevice with a threephase stator may be employed having coils I56, I51and I58, Y-connected for example. The rotor in the arrangementillustrated comprises a winding I59. Since the device is operated singlephase, only one or two of the stator windings need be employed, and asillustrated, the coils I56 and 7 I51 are connected in series across thesensitivity adjustment potentiometer I 41 and the rotor winding I59 isconnected across the input alternatingcurrent supply, viz., thetransformer secondary winding I31. As shown. the pivoted arm 38 ordancer arm is mechanically connected to the rotor I59. The inventionobviously is not limited to the specific type of variable ratiotransformer employed nor to the connection of the voltage input to therotor and the voltage output terminals to the stator instead of viceversa.

As will be explained more in detail hereinafter, when the minimum orzero voltage appears across the primary windings I43 or I44 of thecalibrating bridge I25, current flows in the direct-current winding IIIof the saturable reactor 93 and the phase responsive rectifiers 19 and80 carry maximum current so as to supply full field to the motor, thusobtaining maximum torque or minimum speed of the motor and facilitatingstarting. This 8 circumstance is taken advantage of to provide automaticsafety arrangements for assuring that all motors of the multiple-blockwire drawing machine will have maximum torque and a minimum speed whenthe apparatus is started up. Accordingly, a pair of normally closedcontacts IN is connected across transformer windings I43 and I44 of thecalibrating bridge I25. The contacts I6I constitute stationary contactscooperating With a movable contact I62 carried by a plunger I63 ininductive relation to a winding I64 connected to a. suitable powercircuit, for example, across the armature brushes of the motor inquestion, viz., the motor 24. (See Fig. 2.) Similar normally closedcontacts are provided for the motors 22 and 23. but have been omittedfrom the description and drawing for the sake of simpliclty.

A conventional arrangement, not shown, is likewise provided for themotor 25 to shunt out its manual field control resistor 64 when theapparatus is started.

Referring to Fig. 1, the first operation in starting the machine is, ofcourse, starting a tapered end of wire through the dies I4, I5, etc.This operation is conventional and need not be further described. Afterthe wire has been passed around the capstans and the movable pulleys 3I,and upon supplying power through the armature, the normally closedcontacts such as the contacts IBI are initially closed. This gives themotors maximum field and maximum torque. As soon as the motors have comeup to speed sufficiently to produce a predetermined back voltage acrossthe armature, the winding IE4 is energized opening the contacts I6I andthe operation of each of the automatically controlled motors 22, 23 and24 proceeds under the control of the electronic field control circuits,such as that for the motor 24 illustrated in Fig. 3.

Referring to Fig. 1, if the capstan I1 is not rotating rapidly enough inrelation to the capstan I8, the wire is being drawn into the die 2I morerapidly than it leaves the capstan I1. In other words the wire or otherfilar element in the rear is not being supplied rapidly enough inrelation to the portion thereof in advance. Accordingly, the wire loop33 is being shortened and the dancer arm 38 is drawn downward (withrespect to the position illustrated in Fig. 1). This rotates the rotorI59 of the Selsyn type variable ratio transformer 42 toward the positionin which the voltage output of the windings I56 and I51 is greater;accordingly, a greater voltage appears in the potentiometer I41. Thevoltage supplied to the primary windings I43 and I44 of the transformersI48 and I49 is increased and a greater voltage appears on the controlelectrodes I28 and I29 of the tubes H2 and H3. This decreases theaverage potential of the control grids, for the following reason. Thecharacteristics of the tubes II2 and II 3 are such that the grids cannotrise above cathode potential during positive half cycles of the controlgrid volt ge, and accordingly ony the negative half cycles of controlgrid voltage are effective. The output of the tubes H2 and I I3 isdecreased with decreasing average grid potential, thus decreasing theflow of direct-current through winding II I of the saturable reactor 83.This in turn increases the reactance of this winding and increases thephase shift produced by the phase adjusting bridge 82.

Thereupon the anodes and the control grids of the thyratron tubes 19 andare brought out of phase, the current output thereof is decreased.

9 the field strength of the motor 24 is decreased and the speedincreases. This enables the capstan I1 to supply wire at a greater speedand enables the wire loop 33 to increase in length again until thedancer arm 38 has found an angular position at which the ratio of thespeed of the capstan I1 to the speed of the capstan I8 equals thereciprocal of the draft through the wire die 2 I.

In a similar manner the speed of the capstan I6 is automaticallyadjusted to take the proper relation to the speed of the capstan I1 andthe speed of the capstan II is adjusted to take proper relation to thatof the capstan I6. Excessive speed change and overshoot are avoided byreason of the anti-hunt or anticipating circuits in the grid control 84.Thus, it the arm 38 should be moved abruptly as a result of an abruptchange in the manual setting of the motor 25 or for another reason, adegenerative or opposing change in control voltage of the grids I28 andI29 will be produced as a result of the change in current flow throughthe partially degenerative cathode resistor H applied to differentiatingcircuit II'I-IIB, partially modified by the integrating circuit II9-I2Il. These circuits are so connected that they produce an opposingeffect which increases with abruptness of the actual change and holdsback the speed correction of the motor in order to enable conditions tostabilize.

The manner in which the phase responsive rectifiers 19 and 86 functionto control field current in response to variations in phase of the gridsis illustrated in Figs. 4a. to 4d, wherein the sine wave curves I65illustrate the voltage applied to the anode of one of the tubes. forexample the anode 85 of the tube 19, by the transformer winding 18. Thedotted sine wave I66 represents the voltage applied to the control grid89 from the phase shifting bridge network 82 when the current flowing inthe winding III of the saturable reactor 83 is such as to balance thereactance of the winding 99 against the resistance of the winding 98 andproduce a quadrature relationship between the grid voltage I66 and theanode voltage I65. As will be understood by those skilled in the art,the current flow in the tube 19 is extinguished whenever the anodevoltage I65 falls below zero. The flow of current can be resumed againwhen the anode voltage I65 rises above zero only when the grid potentialis above a predetermined value, ordinarily slightly below but quiteclose to zero and depending upon the amplitude of the anode voltage.

Thus in the case illustrated in Fig. 4a, the control grid voltage I66does not reach the ignition voltage until at or very nearly at the timecorresponding to one-quarter wave length after the beginning of the waveI65. Thereupon the tube 19 becomes conducting and remains conducting, asillustrated by the shaded portion of the sine wave I61, until the waveI65 falls to zero. If the control grid voltage had lagged less behindthe anode voltage, as illustrated by the dotted sine wave I68 in Fig.4b, the tube would have become conductive sooner, as illustrated by theshaded portion I69. Since the tube is conducting for a longer period oftime, the average current flow is greater and the average direct-currentflowing through the motor field is greater, resulting in lower motorspeed and resulting in degenerative braking if the motor has beentraveling at a speed greater than the running-light speed which would beproduced by the new field adjustment illustrated in Fig. 4b.

On the other hand, it the control grid voltage is considered to lagconsiderably behind the anode voltage, as illustrated by the dotted sinewave III in Fig. 4d, the tube conducts current for a relatively shortportion of the cycle represented by the shaded area I12, and the averagefield current is reduced and the motor speed is increased. At starting,when the windings I43 and I44 are short-circuited by the normally closedcontacts I6I, a maximum current flows through the tubes I I2 and I I3.The core of the saturable reactor 83 is so highly saturated that it hasnegligible reactance so that the output voltage is very nearly in phasewith the input voltage, that is to say, the anode and the grid voltagesof the thyratron tubes are very nearly in phase, as illustrated in Fig.4c, and maximum current full field is produced as shown by the shadedarea I13.

In Fig. 5a the curve I16 represents the anode voltage applied by thetransformer winding I33 to one of the vacuum tubes, for example, thevacuum tube H2. The tube does not conduct current through the negativehalf cycles of anode voltage so that the potential of the grid duringsuch negative half cycles is immaterial. The grid voltage cannot riseabove cathode voltage during the positive half cycles of the anodevoltage because grid current would then start to how, resulting involtage drop through the current limiting resistor I55. Accordingly, thecurrent output of the tube is determined by the amplitude of thenegative voltage applied to the control grid during the positive halfcycles of anode voltage. Such tubes conduct current in decreasing valueas the grid potential is reduced or the negative grid voltage is madegreater to a certain value called the "cut-off" value at which thecurrent flow becomes zero. Thus, as illustrated in Fig. 521, when thevoltage input to the control grid I28 is substantially zero, as shown bythe dotted line I11, a maximum anode current half cycle is produced. Onthe other hand, with progressively greater values of control gridvoltage represented by increasingly large-amplitude sine waves I18, I19and ISO, progressively smaller values of anode current are caused toflow, as represented by the progressively smaller shaded areas IBI, I82and I83.

The voltage output of the variable ratio transformer 42 is tapped off bythe adjustment contact I46 of the potentiometer I41, of the calibratingbridge I25 shown in Fig. 3. Consequently, the amplitude of responseobtained by rotation of the rotor I59 depends upon the position of thetap I46. Accordingly, this potentiometer serves as the sensitivityadjustor.

The control grid voltage for the tubes H2 and I I3 is taken from thetransformers I48 and I49 and these are connected in the bridge cross armbetween the center tap I48 of the supply winding I31 and the adjustabletap I45 of the position adjusting potentiometer I39. Therefore, themagnitude and phase of the voltage output of the variable ratiotransformer 42, required to produce zero voltage output from thewindings I5I and I52, depend upon the angular position of the tap I45.For example, if this is placed at such a position that its potentialequals the potential of the center tap I38, the voltage output of thewindings I5I and I52 will be zero when the rotor I 59 is in apredetermined angular position with respect to the stator windings I58and I51. Rotation of the dancer arm 38 in a given direction will thenincrease the voltage, and rotation of the dancer arm in the oppositedirection will alsoincrease the voltage but in opposite phase relation.

Ii it is desired to set back the angular position of the dancer arm 38,which results in zero voltage output at the windings I51 and I52, thisis accomplished by moving the potentiometer adjustable tap M to the leftso as to increase the joutput potential of the windings vliil and 152with respect to the tap I48 of the potentiometer H1. Accordingly, it isthen necessary for the arm '38 to move back introducing an out-ofphasepotential neutralizing that produced by the arm I15 of the positionadjusting potentimeter 15!) in order to obtain a zero output thewindings 1 5i and I52. Likewise, moving the arm in the oppositedirection, via, in the direction of "the arrow I, has the effect ofadvancing the position of the arm [33 at which a predetermined currentflow from the tubes H2 and H5 is obtained.

"It will thus be observed that a fully electrical control is obtainedand no mechanical adjustments whatsoever are required ior adjusting theangular positions of the dancer arms at which they maintain the desiredspeed relation, nor for adjusting the angular movement of the dancerarms required to produce predetermined variations in speed, as theseadjustments are accomplished electrically by the potentiometers 1'39 andM1. Furthermore, the adjustment of the degree of sluggishness orquickness o respouse in the change of motor speed and the change inspeed of the draft of wire by the succeeding capstan, is accomplished byadjustment of the anti-hunt potentiometer arms I23 and i2 1 to give thedesired degree of first and second order anticipation. In this mannerovershoot in the correction of speed, and, therefore, hunting areovercome. Since the control of motor speeds is fully automatic and maybe made to respond very rapidly without hunting, wire may be drawnsafely and reliable at very high rates of speed.

Certain embodiments of the invention and certain inethcds'of operationembraced therein have been shown 'and'particularly described for thepurpose of explaining the principle of operation-of the' invention andshowing its application. but it wi ll be dbvi'ous to those skilled inthe art that many modifications and variations are possible, and it isintended, therefore, to cover all *suchmodifications and variations astall within the scope of the invention which is defined in the claimsappended hereto and to my co pending divisional application, Serial No.347,188, 'filedApril 6, 1953.

'1. A control system for motors driving a filar element, said systemcomprising in combination a'plurallty of motor field windings, theenergization of which controls the speed of each of a pluraiity ofsuccessive portions of the filar element being supplied to a portion inadvance. variable-ratio transformers each having a rotor the position ofwhich determines the voltage ratio, each rotor being actuated by tensionon said filar element at one of the successive portions thereof,vacuum-tube type direct current controllers each having controlelectrode means excited by the output of one 05 said variable ratiotransformers, degenerative resistors for each of said controllers,anti-hunt differentiatlug circuits interposed between saidvariableratioj transformer outputs and the control electrodes, saturablereactors each having a directcurrent winding supplied by one of saiddirectcurrent controllers, resistance-resistance type phase adjusters,each having a variable-reactance arm comprising one of said saturable{reactors, thyratron type variable-current rectitiers each havingcontrol electrode means excited by the output of one of said phaseadjusters. said thyratron type rectifiers each having output,connections supplying one of said field windings. whereby the angularposition of each said rotor is determined by the tension of one of thesuccessive portions of the filar element, and in turn determines thevoltage output of the associated variable voltage transformer, thedegree of saturation of the associated saturable reactor, the phaseangle of the control electrode means of the associated tbyratrcn typerectifier, the energization of the field winding controlling the speedof such portions of the filar element and therefore determines the speedthereof, the connections being such that decreased tension brings aboutdecrease in driving speed and an increasd tension brings about theincrease in driving speed, whereby the speeds of all portions of thefilar element except for the portion in advance are automaticallyadjusted to supply the filar element at the speed required by the speedof the portion of the filar element in advance.

2. A control system for the field winding of a motor driving a filarelement supplied to a driven portion thereof which is in advance,comprising in combination a field winding, the energizetion of whichcontrols the speed of the filar element, a transformer with relativelymovable I windings having a motor the position of which rotor, saidrectifier having an output connection for supplying field current,whereby the rotor position is determined by the tension of the filarelement and in turn determines the output of the transformer, the outputof the rectifier, the strength of the field and therefore the speed ofthe filar element, the connections being such that decreased tensionbrings about decreases in speed and increased tension brings aboutincrease in speed, whereby the speed is automatically adjusted to supplythe filar element at the speed required by the speed of the petition inadvance.

3. A control system for the field winding of a motor driving a filarelement supplied to "aoiriven portion thereof which is in advance,comprising in combination, a variable ratio transformer having a rotorbeing movable in response to variations in tension, a vacuum-tube typedirectcurrent controller having control electrode means excited by theoutput of said variable ratio transformer, a degenerative resistor dorsaid controller, an anti-hunt differentiating circuit interposed betweensaid variable ratio transformer output and the control electrode means,a saturable reactor having a direct-current winding supplied-by saiddirect-current controller, a resistance-reactance type phase adjustingbridge, said saturable reactor having an alter11ating-current windingforming a variable reactance arm for said phase adjustingbridge, athyratron type variable-current rectifier having control electrode meansexcited by the output of said phase adjustor, said thyratrontype-rectifier having an output connection supplying field currentwhereby the rotor position is determined by the tension of the filarelement and in turn determines the voltage output of the variablevoltage transformer, the degree of saturation of the saturable reactor,the phase angle of the control electrode means of the thyratron typerectifier, the strength of the field and therefore the speed of thefilar element, the connections being such that increased tension bringsabout decrease in speed and increased tension brings about increase inspeed, whereby the speed is automatically adjusted to supply the filarelement at the speed required by the speed of the portion in advance.

4. A control system for the field winding of a motor driving a filarelement supplied to a driven portion thereof which is in advance,comprising in combination, a variable ratio transformer having a rotorthe voltage of which determines the voltage ratio, said rotor beingmovable in response to variation in tension of the filar element. avacuum-tube type direct-current controller having control electrodemeans excited by the output of said variable ratio transformer, asaturable reactor having a direct-current winding supplied by saiddirect-current controller, a resistance-reactance type phase adjustingbridge, said saturable reactor having an alternating-current windingforming a variable reactance arm for said phase adjusting bridge, athyratron type variable-current rectifier having control electrode meansexcited by the output of said phase adjustor, said thyratron typerectifier having an output connection supplying field current wherebythe rotor position is determined by the tension of the filar element andin turn determines the voltage output of the variable voltagetransformer, the degree of saturation of saturable reactor, the phaseangle of the control electrodes of the thyratron type rectifier, thestrength of the field and therefore speed of the filElI' element, theconnections being such that reduced tension brings about decrease inspeed and increased tension brings about increase in speed, whereby thespeed is automatically adjusted to supply the filar element at the speedrequired by the speed of the portion in advance.

5. A control system for the field winding of a motor driving a filarelement supplied to a driven portion thereof which is in advance,comprising in combination, a phase-responsive variable current rectifierfor supplying field current, a bridge type resistance-reactance phaseadjustor having a variable phase output connected to said rectifler forcontrolling the phase of the excitation thereof, and a mechanismresponsive to the tension of the filar element for varying the reactanceof the reactance arm of said phase adjustor, whereby the tension of thefilar element determines the reactance of the phase adjustor, the phaseangle of the excitation of the rectifier, and the strength of the fieldcurrent and therefore the speed of the filar element, the connectionsbeing such that decreased tension brings about decrease in speed andincreased tension brings about increase in speed, whereby the speed isautomatically adjusted to supply the filar element at the speed requiredby the speed of the portion in advance.

6. A control system for motors driving a filar element, said systemcomprising in combination a plurality of motor field windings, theenergization of which controls the speed of each of a plurality ofsuccessive portions of the filar element being supplied to a portion inadvance, a phase-responsive variable current rectifier for supplyingcurrent to each of said field windings, a phase adjuster for controllingthe phase of the excitation of each such rectifier, and mechanismresponsive to the tension of each such portion of the filar element foradjusting the phase of the output of the phase adjuster associated withthe preceding portion, whereby the tension of each portion of such filarelement determines the phase of the phase adjustor controlling the fieldcurrent, and therefore determines the speed of such portion of the filarelement, the connections being such that decreased tension brings aboutdecrease in speed and in-- creased tension brings about increase inspeed, whereby the speeds of all the portions of the filar elementpreceding the portion in advance are automatically adjusted to supplythe filar element at the speed required by the speed of the portion inadvance.

7. A control system for the field winding of a motor driving a filarelement supplied to a driven portion thereof which is in advance,coinpris ing in combination, connections for supplying field current, avariable effective impedance discharge path interposed in saidconnections, electrode means for controlling the effective impedance ofsaid discharge path, a mechanism responsive to tension of the filarelement for varying the relation of the voltage of said controlelectrode means to supply voltage at said field input connections forcontrolling the field current whereby continuously variable fieldcontrol responsive to infinitesimal variations in tension is obtained,the tension-responsive mechanism determining the field strength and thespeed of the said filar element, the connections being such thatdecreased tension brings about decrease in speed and increased tensionbrings about increase in speed, whereby the speed of the filar elementis continuously adjusted to supply it as required by the speed of theportion in advance.

WILLIAM FEW. JOHN D. SAUTER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,068,970 Winograd Jan. 26, 1937 2,153,192 Koontz Apr. 4, 19392,192,785 Bonds Mar. 5, 1940 2,252,352 Pierce Aug. 12, 1941 2,320,833Schoults et al June 1, 1943 2,321,612 Nye June 15, 1943 2,370,481 MorganFeb. 27, 1945 2,404,641 Leigh et al. July 23, 1946 2,421,632 LivingstonJune 3, 1947 2,445,454 Puchlowski July 20, 1948 2,484,825 Harris Oct.18. 1949

